The present invention relates to an information recording method and an information recording apparatus using a reversible phase change caused by light irradiation, and in particular to an information recording method (using reversible phase change) capable of single beam overwriting i.e., capable of recording new information with a single beam spot while erasing information already recorded and capable of rewriting without leaving incompletely erased information called "unerased information" and an optical information recording apparatus using a rewritable phase change reversible optical disk.
A rewritable optical information recording apparatus using a recording film which changes in phase between a crystalline state and an amorphous state is already known. In such an apparatus, a high-power optical beam spot corresponding to the information to be recorded is irradiated onto a recording film to locally raise the temperature of the recording film. A phase change between the crystalline state and the amorphous state is thus caused to record the information. A resulting change in optical constant is read as a change in intensity of reflected light of a low-power light beam, the recorded information being thus reproduced. For example, a reversible optical disk having a phase change recording film is rotated and a light beam spot is condensed onto the recording film to raise the temperature of the recording film above its melting point as described in Proceedings of Spring Conference of the Japanese Society of Applied Physics, 7, p-x-l, (1983). After the optical beam spot has passed, that portion of the recording film is quenched to turn that portion into the amorphous state, information being recorded. And erasing is performed by irradiating an elliptic light beam which is longer in the beam travelling direction so as to keep the temperature of the recording film within a crystallizable temperature range which is not lower than the glass transition point and which is not higher than the melting point for a long time sufficient to promote the crystallization.
Further, double-beam pseudooverwriting (recording new information after data already recorded) is performed by arranging an erasing elliptic optical beam spot ahead of a recording circular light beam spot.
In an optical information recording apparatus using a phase change recording film which can be crystallized at high speed, the power of a single circular light beam spot is changed among a plurality of power levels to cause crystallization or amorphizing as described in Proc. SPIE, Vol. 695, pp. 105 to 109 ,1986), for example. That is to say, a part of the recording film irradiated by an light beam having a power capable of raising the temperature of that part assumes an amorphous state when it is cooled. On the other hand, a portion of the recording film irradiated by an light beam having such a power as to raise the temperature of that portion above the glass transition point and below the melting point assumes a crystalline state.
However, it is very difficult to provide a difference between quenching and annealing by passing a single light beam spot through the recording film once. The prior art of raising the light beam in accordance with information to be recorded for rewriting the information had a problem that an incompletely erased portion remains after over writing. In phase change optical disks, recording films which are not processed yet after the vapor deposition are not uniform in many cases when seen in minute space ranges. Initialization for attaining uniformity is thus required. In the initialization, an optical beam of high power is irradiated to raise the temperature above the melting point once. In addition, a part to be recorded must be turned into an amorphous state or a crystalline state in some recording methods. The necessity for such initialization results in a problem of inconvenient use.